doc: fix formatting of notes in meson guide
doc: fix formatting of notes in meson guide

The "note" callouts in the chapter describing the meson build were
incorrectly formatted, so adjust to use the correct markdown syntax.

Fixes: 9c3adc289c5e ("doc: add instructions on build using meson")
Cc: stable@dpdk.org

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>
Acked-by: John McNamara <af31595c36a4239b9676e9b3a777d3e2f15a6c4d@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk